1. Field of the Invention
The present disclosure relates to a vacuum circuit breaker, and particularly, to terminals for a vacuum circuit breaker capable of performing an electric insulating performance even if a distance between a first terminal of a breaker body and a second terminal of a cradle is short at a test position, capable of minimizing impacts of terminals due to an elastic load occurring when terminals are connected to each other, and capable of minimizing vertical vibrations of the breaker body and noises occurring when the terminals are connected to each other or are disconnected from each other, and a vacuum circuit breaker having the same.
2. Background of the Invention
Generally, a vacuum circuit breaker is an electric apparatus for protecting an electric power circuit and a load device, by opening or closing the circuit when a high voltage is applied to the circuit, and by breaking the circuit in the occurrence of an abnormal current such as a short circuit current.
The vacuum circuit breaker is being widely used at a power station, a substation, a power distribution station and a power transmission site. The vacuum circuit breaker may be individually used. Alternatively, the vacuum circuit breaker is used in an accommodated state in an electric power distributing and supervising board together with other instruments for supervising electric power.
The vacuum circuit breaker is categorized into a withdrawal type and a fixed type. The present disclosure relates to a withdrawal type vacuum circuit breaker.
The withdrawal type vacuum circuit breaker largely comprises a cradle and a circuit breaker body (abbreviated as breaker body hereinafter).
The cradle is fixedly-installed at the electric power distributing and supervising board, and includes an external terminal portion for connection to an external electric power circuit and an internal terminal portion for connection to a breaker body side terminal (abbreviated as body side terminal hereinafter). The cradle also includes a bottom portion on which the breaker body moves, and a pair of side plate portions having guide rails for guiding mounting and rolling of wheels of the breaker body.
The breaker body includes main circuit units disposed for three poles (in other words three phases) or three, and body side terminals formed of a conductor and electrically connected to the main circuit units, respectively.
The main circuit units include a vacuum interrupter configured by a vacuum container having therein a fixed contact and a movable contact. The vacuum container is formed of a ceramic material, is in a vacuum state, and has an insulating property. The main circuit units are disposed for three poles, and are configured to open or close electric power circuits of the three poles.
Configurations and operations of terminals for the conventional vacuum circuit breaker will be explained with reference to FIG. 1.
FIG. 1 is a longitudinal sectional view showing a configuration of terminals in accordance with the conventional art. Referring to FIG. 1, the terminals for the conventional vacuum circuit breaker include a first terminal 30 and a second terminal 40.
Referring to FIG. 1, reference numeral 50 designates a safety shutter apparatus supported by a cradle 20, installed in front of the second terminal 40, and movable to an opening position for allowing the first terminal 30 to be connected to the second terminal 40 or a closing position for preventing an access of the first terminal 30 to the second terminal 40. The operation of the safety shutter apparatus 50 to the opening position or the closing position interlocks with a moving operation of a breaker body (not shown) to a connection position, a test position and a disconnection position. The connection position indicates a position where the first terminal 30 of the breaker body and the second terminal 40 of the cradle 20 are connected to each other. The test position indicates a position where the first terminal 30 of the breaker body and the second terminal 40 of the cradle 20 are disconnected from each other, but an electric control power source for testing an opening or closing operation is supplied to a controller of the breaker body. Here, the safety shutter apparatus 50 is disposed at a closing position, and the first terminal 30 is close to the safety shutter apparatus 50 as shown in FIG. 1. The disconnection position indicates a position where the first terminal 30 of the breaker body and the second terminal 40 of the cradle 20 are disconnected from each other, and the electric control power source for testing an opening or closing operation is not supplied to the controller of the breaker body. Here, the safety shutter apparatus 50 is disposed at a closing position, and the first terminal 30 is distant from the safety shutter apparatus 50.
Configurations and operations of a driving apparatus of the safety shutter apparatus 50 have been disclosed in Korean Patent Registration No. 10-0451372 registered by the present applicant (Title of the invention: Shutter driving apparatus of cradle for vacuum circuit beaker), and thus detailed explanations thereof will be omitted.
Firstly, the first terminal 30 is installed at the breaker body, and includes a pair of supporting plates 31, a plurality of finger contactors 32, and a plurality of ring springs 33.
The first terminal 30 is also called a tulip terminal, because the plurality of finger contactors 32 disposed in a radial direction have a tulip shape.
The pair of supporting plates 31 are means for supporting the plurality of finger contactors 32, and are configured by ring-shaped iron discs having a predetermined thickness.
The plurality of finger contactors 32 are finger-shaped conductor contactors, and are radially installed on an outer circumferential surface of the supporting plates 31. Each finger contactor 32 has a pair of insertion recess portions for inserting an outer circumferential surface of the supporting plates 31, a pair of contact protrusion portions, and a plurality of spring accommodation recess portions for accommodating a plurality of ring springs 33 therein.
The plurality of ring springs 33 are accommodated in the spring accommodation recess portions of the finger contactors 32, and provide an elastic force to the finger contactors 32 toward the center of a circle formed by the radially installed plurality of finger contactors 32. When an outer circumferential surface of the second terminal 40 of the cradle has been contacted with an inner circumferential surface of the first terminal 30 formed by the contact protrusion portions of the finger contactors 32, an elastic force of the ring springs 33 serves to maintain a contact pressure between the first terminal 30 and the second terminal 40.
As shown in FIG. 1, the first terminal 30 may further include a connection conductor 35, an insertion member 36, a pressing plate 37, a coupling screw 38 and a housing 34.
The connection conductor 35 is a conductor extending to the main circuit units of the breaker body of the vacuum circuit breaker, and electrically connected to the main circuit units. And, the connection conductor 35 may be configured by a pipe-shaped conductor.
The insertion member 36, the pressing plate 37 and the coupling screw 38 are elements for coupling the plurality of finger contactors 32 to the connection conductor 35.
The insertion member 36 has an insertion portion inserted into the connection conductor 35 and connected to the connection conductor 35 by a pin (not shown), and a flange portion outward extending from one end of the insertion portion in a radial direction. The flange portion has a recess portion.
The pressing plate 37 is inserted into the recess portion of the flange portion of the insertion member 36, as the tighten the coupling screw 38 thereby adhering the flange portion of the insertion member 36 to an inner surface (refer to inner surface of left end portion of finger contactor 32 in FIG. 1) of one end of the finger contactors 32 through the pressing plate 37.
The coupling screw 38 is the element for adhering the flange portion of the insertion member 36 to an inner surface of one end of the finger contactors 32 by inserting into the insertion portion of the insertion member 36.
The housing 34 accommodates therein the connection conductor 35, the insertion member 36, the pressing plate 37 and the coupling screw 38, thereby providing a case for accommodating therein part of the finger contactors 32.
Referring to FIG. 1, the second terminal 40 is fixedly-installed at a rear vertical plate 20a of the cradle, and is configured by a bushing-type electric conductor. The second terminal 40 may be fixed to the rear vertical plate 20a without being moved up and down, by supporting plates 41 for supporting upper and lower surfaces of the second terminal 40 on front and rear surfaces of the rear vertical plate 20a, and by connection bolts 42 for fixing the supporting plates 41 to the rear vertical plate 20a. 
Referring to FIG. 1, reference numeral 43 designates a screw opening.
An outer diameter of the second terminal 40 is larger than an inner diameter of an inner circumferential surface of the first terminal 30 formed by an inner side surface of each finger contactor 32.
When the second terminal 40 and the first terminal 30 operate to a connection position from a test position, each finger contactor 32 of the first terminal 30 is outward widened in a radial direction within a short time due to collision with the second terminal 40. Here, part of the breaker body having the first terminal 30 is lifted up to fall down, i.e., has vertical vibrations. This may cause vibration noises, and damages of a terminal portion and the breaker body.
Furthermore, as the finger contactors 32 are outward widened in a radial direction during a connection operation, a larger elastic force of the ring spring 33 is required so as to reduce an electric resistance by maintaining a contact force between the finger contactors 32 and an outer circumferential surface of the second terminal 40.
Besides, in order to obtain a predetermined electric insulating distance between the first terminal 30 and the second terminal 40, the second terminal 40 has to be formed to have a short length. This may cause a front surface of a leading end of the second terminal 40 to be almost perpendicular to an outer circumferential surface of the second terminal 40. As a result, the second terminal 40 may collide with the first terminal 30 during an initial operation toward a connection position. This may cause part of the breaker body having the first terminal 30 to be lifted up to fall down (i.e., to vertically vibrate). As a result, noise may occur and the terminal portion and the breaker body may be damaged.
Furthermore, the vertical vibrations and noises also occur when the breaker body is backward moved to a test position from a connection position.